1. Field of the Invention
The present invention relates to a display device and method of fabricating a display device, and more particularly, to a high aperture ratio liquid crystal display device and method of fabricating the same.
2. Discussion of the Related Art
Presently, many types of flat panel display (FPD) devices are actively being developed because of their portability and low power consumption. Among the many types of FPD devices under development, liquid crystal display (LCD) devices are increasingly used as monitors for notebook computers and desktop computers because of their high resolution, ability to display colored images, and superior ability to display moving images.
In general, the LCD devices include two substrates, each having electrodes that face each other, and a liquid crystal layer interposed between the electrodes. When a voltage is supplied to the electrodes, an electric field is generated to modulate light transmittance of the liquid crystal layer by reorienting the liquid crystal molecules, thereby displaying images.
Since the liquid crystal layer does not emit light itself, an additional light source is necessary. Thus, a backlight unit is disposed under an LCD panel to display images by adjusting the amount of light emitted from the backlight unit according to an alignment of the liquid crystal molecules. Accordingly, the electrodes of the two substrates may be formed of transparent conductive material, and the two substrates may be formed of transparent material. Thus, the LCD device is commonly referred to as a transmissive-type LCD device that displays bright images under dark surroundings due to the backlight unit.
FIG. 1 is a schematic cross sectional view of a transmissive-type liquid crystal display device according to the related art. In FIG. 1, first and second substrates 10 and 40 are spaced apart from each other, wherein a gate electrode 12 is formed on an inner surface of the first substrate 10 and a gate insulating layer 14 is formed on the gate electrode 12. An active layer 16 and an ohmic contact layer 18 are subsequently formed on the gate insulating layer 14 over the gate electrode 12. In addition, source and drain electrodes 24 and 26 are formed on the ohmic contact layer 18 to constitute a thin film transistor (TFT) “T” with the gate electrode 12. Similarly, a data line 22, which is connected to the source electrode 24, formed of the same material as the source and drain electrodes 24 and 26 is formed on the gate insulating layer 14.
In FIG. 1, a passivation layer 30 is formed on the data line 22 and source and drain electrodes 24 and 26 to cover the TFT “T.” In addition, the passivation layer 30 has a contact hole 32 exposing the drain electrode 26. Accordingly, a pixel electrode 34 is connected to the drain electrode 26 through the contact hole 32 and is formed on the passivation layer 30 in a pixel region (not shown). Since the pixel electrode 34 covers the TFT “T” and overlaps the data line 22, an aperture ratio is improved. The passivation layer 30 is formed of an organic material having a relatively low dielectric constant in order to prevent signal interferences between the pixel electrode 34 and the data line 22.
A black matrix 42 is formed on an inner surface of the second substrate 40, a color filter layer 44, including red, green, and blue sub-color filters 44a, 44b, and 44c, is formed on the black matrix 42 and second substrate 40, and a common electrode 46 of a transparent conductive material is formed on the color filter layer 44. The black matrix 42 covers the TFT “T” and overlaps an edge portion of the pixel electrode 34, wherein one of the sub-color filters 44a, 44b, or 44c corresponds to one pixel electrode 34. In addition, a liquid crystal layer 50 is formed between the pixel electrode 34 and the common electrode 46.
In FIG. 1, a first optical film 62 is formed on an outer surfaces of the first substrate 10, and a second optical film 64 is formed on an outer surface of the second substrate 40. In addition, a first polarizing plate 72 is formed on the first optical film 62, and a second polarizing plate 74 is formed on the second optical film 64. A backlight unit 80 is disposed outside of the first polarizing plate 72, and includes a light guide plate 86 under the first substrate 10, a light source 82 adjacent to a lateral face of the light guide plate 86, and a reflector 84 surrounding the light source 82.
In the transmissive-type LCD device, the black matrix is formed along the edge portion of the pixel electrode, i.e., the portion corresponding to the gate line and the data line to prevent a light leakage. For example, the black matrix has a width of about 10 um to about 20 um, considering the attachment margin of the first and second substrates. Accordingly, an aperture ratio of the LCD device is reduced to be about 60% to about 70%, thereby reducing brightness.